From my personal experience I have found that it is best to replace the o-rings on the fuel line to the pre filter and on the pre filter whenever they are taken apart. It's cheap insurance to prevent a fuel leak. Sometimes all it takes is a slight movement of these plastic fuel lines to make the o-rings start to leak.
I have also found that sometimes the o-rings from aftermarket suppliers are not the correct size and have had to get the correct parts from the dealer.

As far as the hold down clamp not pushing down hard enough, it's only there to hold the line and filter in place. Both the line and the filter seal by compressing the o-ring around the circumference and should not require much downward force from the clamp.

I would replace those 2 o-rings, clean all the residual fuel from the area and recheck for a fuel leak after a good long test drive, if the o-rings are loose enough to allow air in they will usually leak fuel out also.

Good luck, Robert

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Mercedes Benz Master Tech - Retired

I agree. If once you start it, you can drive it down the road with no fuel starvation issues then you have no fuel starvation issues. No clogged filters, no clogged tank screens.

I don't disagree with replacing the o-rings. But I cannot figure out when they would ever be under pressure to allow fuel to leak out. I think that they could leak air in and never leak fuel out. That is why I suggested temporally installing an electric fuel pump to pressurize the fuel lines. You will find the leak instantly.

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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
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1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO

Maybe the OP doesn't realize there are TWO O-Rings on the prefilter fitting...there is one at the end of the hose which goes into the center and one around the pre-filter itself. Both of those O-Rings have to be air tight and 90% of the problems such as he is having is due to a leak of one or both of them.

I can't stress that enough...you need to make sure that the seal at that housing is perfect or you will lose prime when the tank is below 1/2 full and the nose is point up.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

You are correct, I don't/didn't know there were 2 orings. I ordered the parts from Peachparts. Bought a filter as well, lemme check in the bag and see what I can see.

Is there a diagram posted somewhere I can see where this ring goes?

btw - turning the car off produces air in the prefilter line right away....

ding, ding, ding, ding...we have a winner.

When you pull out the plastic pre-filter the o-ring is around its body (#29 on the diagram below). M-B in their wisdom does not include this ring with the new filters so many times it isn't replaced and causes the trouble. The other ring is on the fuel line fitting which pressed into the top of the pre-filter (#35). You can opt to replace the whole fuel line (#32) which is cheap or just the o-ring (which is cheaper).

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Thanks Marty! This forum rocks.

#35 is the one I didn't change/replace.

I just went out, checked and found that I didn't get that oring with my order.

I do have a assorted box of viton orings, so I tried using one that appeared to be the same size....BIG mistake. I must have sucked a bunch of air in. When I traded it out for the used one, it took forever to get the system primed and then even more time to get it to finally fire off without cranking.

I'm at 1/4 tank or less, and nose waws slightly uphill, so I'm guessing neither one of those things helped either.

Hopefully the correct part will fix the problem - it sure didn't seem like there was a problem with the Oring that was in there before, but it's getting air from somewhere. Maybe I should just order the whole line?

Yes, just order the whole line...they usually are less than $10, that way you are sure you have the right parts. I also always put a little white lithium grease on those o-rings before I install them, it helps them go on easier and improves the seal, IMHO. It takes all of 5 minutes to install the line...just remember any time you remove one of those lines with the white clips on them that when the clip is pushed IN and doesn't wiggle around it is ready to remove or replace, but once the fitting is fully seated the white clip should be pulled back so it is loose (counter-intuitive, I know).

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Quick question for you Marty. Where can I find that program you posted a screen shot of? I need to get the part numbers off all the fuel lines...

http://epc.startekinfo.com/epc/subscribe.jsp

Subscribe to the EPC, then enter your VIN and go to engine, injection pump, fuel filter and lines and the diagram will come up. Click on the parts and the PNs appear to the left of the diagram. Good luck.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Marty, does EPC work with Windows 7 64 bit? I installed JRE as instructed. Launched EPC and clicked to allow download and then nothing happens. Also, In Internet/options/advanced there was no "check box" to uncheck the Java thing as called for in the instructions. I am pulling my hair out trying to get EPC to work.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Thanks again!

Found my parts, but having a tough time sourcing them online. Are most dealer only items? Fuel lines, Copper sealing rings, etc..

W210 300E

Most are dealer only parts. On the bright side they are very cheap and most are stock items.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Sorry, that's out of my area of expertise. I run mine on XP and it is fine...I would guess you will need to check their tech support section to see what it is compatible with.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

OM606.962, 1998-99 E300 Turbo Diesel Plastic injection pump lines
OM606.962, 1998-99 E300 Turbo Diesel Plastic injection pump lines

Fastlane: INJECTION PUMP DELIVERY VALVE SEAL... RUBBER O-RING
http://catalog.peachparts.com/item.wws?sku=0179974148

Fastlane: COPPER SEAL WASHER, SEAL INJECTION PUMP DELIVERY VALVE, 9 X 13 MM
http://catalog.peachparts.com/item.wws?sku=0049974540


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Finally got all the parts in, figured I'd tackle the prefilter line first.

No go, it's still leaking air from somewhere. I did notice that the lip for the clip side on the prefilter line appears to be missing a small portion of lip, almost like someone pryed on it before. However, best I can tell the oring is seated down inside whatever this piece is, and it's secured with the clip. It's not dripping/leaking fuel out of this portion, and after hitting the starter 3-4 times for 10 seconds each, the car came back to life.

I plan on replacing all of the fuel line parts and injector orings/crush washers next week. I'm hoping somewhere down there I can find where it's seeping air in (and leaving a quarter size diesel stain on the ground after an hour or so....